1. Field of the Invention
The present invention relates to a mobility management system in a personal communication system and in particular, a mobility management system in a personal communication system in which the mobility of a communication terminal unit in the field of the personal communication is considered.
2. Description of the Prior Art
As an example of a mobility management system in a conventional personal communication system, a location updating system that updates the content of a location register upon traveling of a subscriber terminal unit among location registered areas is known. Next, a conventional location Ail updating system will be explained. FIG. 14 is a schematic diagram showing the structure of a network of a conventional location updating system. There are various mobile communication systems that have been structured by different communication companies. In each mobile communication system, the service area thereof is subdivided into several sub-areas. These sub-divided areas are designated as location registered areas. To allow a subscriber terminal unit to have a service of the mobile communication network, the subscriber terminal unit is registered in a location register in one of the location registered areas. In other words, when a subscriber terminal unit is initially used in the mobile communication system, the location of the subscriber terminal unit is registered with a database (that is referred to as a location register) in a home memory station. Thereafter, whenever the subscriber terminal 0 5 unit travels and thereby the location registered area varies, the subscriber terminal unit issues a location registration change request. There are two types of location registers that are a home location register (HLR) and a visiting location register (VLR). These location registers manage location registration information corresponding to the terminal number of each subscriber terminal unit. When a call is made to a subscriber terminal unit, the location registered area of the subscriber terminal unit is searched and the call is directed to the searched location registered area. When communication companies of adjacent mobile communication systems tie up for a roaming service, even if a subscriber terminal unit enters the service area of a mobile communication system to which the unit does not subscribe, with a location registration change request, the location registration information of the home location register of the communication company to which the subscriber has subscribed and the visiting location register of the tied-up communication company can be updated. In addition, when the mobile terminal unit is accepting the roaming service, roaming number is temporarily assigned to the subscriber terminal for identifying the terminal and the roaming number is managed in location registers. Thus, even if the subscriber terminal unit enters any service area, the location thereof is updated and connection to the called subscriber terminal unit is enabled.
In FIG. 14, it is assumed that after the subscriber of terminal unit 71 makes a subscription contract with a communication company which operates the mobile communication system having the service area of area 81, subscriber information of terminal unit 71 is stored in a subscriber memory of home location register 74 and managed therewith. When terminal unit 71 travels from location registered area 82 in area 81 to location registered area 83 in area 81, terminal unit 71 causes visiting location register 76 of mobile communication exchanger 73 to change the registered location of terminal unit 71. Visiting location register 76 assigns location registration information and a roaming number to terminal unit 71. Visiting location register 76 informs home location register 74 of the location registration information and the roaming number assigned to terminal unit 71. Thus, home location register 74 updates the location registration information of terminal unit 71 and assigns the roaming number to terminal unit 71 corresponding to the information received from visiting location register 76. In this state, when mobile communication exchanger 72 receives calling (originating) signal to terminal unit 71, mobile communication exchanger 72 asks home location register 74 for location information of terminal unit 71. Thus, mobile communication exchanger 72 knows that terminal unit 71 is traveling in location registered area 83 that is under the control of mobile communication exchanger 73. In addition, mobile communication exchanger 72 receives the roaming number for the call in from home location register 74 and makes mobile communication exchanger 73 performs the process for call in to the terminal unit 71 represented by the roaming number. Receiving call in from mobile communication exchanger 72, mobile communication exchanger retrieves location registered area 83 in which terminal unit 71 exists and the terminal number of terminal unit 71 by locating the roaming number in visiting location register 76. The terminal number may be a temporary number for a security reason. Mobile communication exchanger 73 calls terminal 71 in a call area, namely the location registered area 83. When terminal unit 71 responds to the call, mobile communication exchanger 73 connects the call in line and a communication channel to terminal unit 71 so as to start a communication between the caller and the terminal unit 71. The call area is normally the same as a location registered area. When a subscriber terminal unit makes a call, the registered location thereof may be automatically changed in a mobile communication exchanger and location registers.
Such a location updating system is explained in, for example, Japanese Patent Laid-Open Publications 07-264653, 07-162942, 07-129488, 06-209489, 03-283898, 02-095037 and GSM system standard (ETSI/TC GSM, Released by ESTI/PT, Released in March, 1990), PDC (Personal Digital Cellular) system standard, and IS-95 system standard (TIA/EIA/IS-95, July 1993). Next, location updating systems explained in these Patent Laid-Open publications and documents of these standards will be explained in brief.
In Japanese Patent Laid-Open Publication 07-264653, a technology of a mobile telephone system is disclosed. In this system, a mobile telephone used as an independent mobile telephone and a cordless telephone which subordinates to a parent telephone is included therein. When the mobile telephone is switched to the cordless telephone, the telephone number of the parent telephone is automatically registered as call in transfer information with a location register that manages location information in the mobile telephone system. When a call is made to the mobile telephone set, the call is transferred to the parent telephone.
In Japanese Patent Laid-Open Publication 07-162942, a technology of a system that has a plurality of mobile communication exchangers that control routing of calls in the same location registered area is disclosed. In this system, when a call is disconnected, a routing number of a subscriber terminal unit is updated in a location register. Thus, in the same location registered area, an optimum routing number can be updated.
In Japanese Patent Laid-Open Publication 07-129488, a technology of a local area mobile communication system is disclosed. In this system, the location of a terminal unit is updated between local area networks.
In Japanese Patent Laid-Open Publication 06-209489, a technology of a radio communication system is disclosed. In this system, when terminal units are concentrated in a particular controlling station, a management station that manages location information of the entire service area shares the load with the controlling station so as to prevent the controlling station from congesting.
In Japanese Patent Laid-Open Publication 03-283898, a technology of a radio communication system that has a plurality of home location registers is disclosed. In this system, when there are many calls in a visitor area other than a home area, the calls are controlled with a home memory on the visitor side as if these calls are in the home area. Thus, the number of occurrences of accessing operation to a home location register is reduced, thereby preventing the home location register from congesting.
In Japanese Patent Laid-Open Publication 02-095037, a technology of a radio communication system is disclosed. In this system, location registration information is locally managed in a radio base station in a zone in which a mobile station is present. When a call is made to a mobile telephone, call in information is sent to all base stations. Each base station searches the mobile telephone with location registration information managed therein and determines whether or not to call the mobile telephone.
In the GSM system standard, a registered location can be deleted and a new location can be registered.
In addition, as another example of the mobility management system in the personal communication system, there is a location tracking system that manages the mobility of subscribers as well as terminal units. Next, this location tracking system will be explained. FIG. 15 is a schematic diagram showing the structure of the location tracking system in a personal communication system. In a personal communication system, when each subscriber subscribes to the network, the subscriber is assigned a unique personal number, namely a unique subscriber number. In a mobile communication system, a tracking object is a subscriber. Terminal units that the subscriber will use are registered corresponding to the schedule which is determined for months, days, days of the week, and time. When a call is made to the subscriber, a terminal unit designated corresponding to the schedule is called. Subscriber information for tracking the location of the subscriber is managed by a home database (HDB). The subscriber information includes, for example, a subscriber number assigned to each subscriber and a subscriber certification number assigned to each subscriber. The home database manages terminal numbers of a plurality of call in terminal units that will be used corresponding to the schedule of each subscriber. In FIG. 15, it is assumed that a home database 86 of a home network 87 manages subscriber numbers, subscriber certification numbers, date and time of schedule, and terminal numbers used corresponding to the schedule for each subscriber as a part of subscriber information. In addition, it is assumed that the home database manages a primary terminal unit and a secondary terminal unit that will be used corresponding to the schedule. When the communication network 88 calls the subscriber at a certain date/time on the schedule, the home network 87 asks the home database 86 for the destination of the call corresponding to the subscriber number as well as the data/time. At this point, home network 87 performs a call in process with the terminal number of primary terminal unit 92 received from the home database 86. In this case, a communication network 89 is selected for call in. When terminal unit 92 in communication network 89 is busy or does not respond, home network 87 receives the terminal number of secondary terminal unit 93 from home database 86 and performs a call in process for secondary terminal unit 93. In this case, a communication network 90 is selected for call in. When terminal unit 93 in communication network 90 responds to the call in, home network 87 connects a communication channel between communication network 88 as the call out (terminating) network and communication network 90 as the secondary call out so as to start a communication between terminal unit 91 and terminal unit 93.
As technical papers that describe technologies of such a location tracking system, there are Japanese Patent Laid-Open Publication 05-308674 and "An intelligent location tracking method for personal and terminal FPLMTS/UMTS communications". In the former, a technology for presuming the transfer of a subscriber and executing a call in to the subscriber even if location information is lost is disclosed therein. In the latter, a technology of generating location tracking pattern information by learning location updating events for a certain period is disclosed.
In a conventional location updating system in a personal communication system, even if a subscriber terminal unit is present in a location registered area to which location information is updated most recently, in case that the unit is in a building that shields a radio wave, a call in to the unit may not be reached thereto and the call in may be abandoned. In this case, the caller may hear a message saying that the objective person is out of the network. Thus, the caller will retry to call another terminal unit through which the caller supposes communication will be established.
In a conventional location updating system, when a subscriber is not present in a communication network areas to which location may be updated and is present in a communication network area to which location may not be updated, the call is abandoned.
To prevent the above-explained invalid call, detaching method may be introduced. In this method, when the subscriber terminal unit goes out of the service area of the network or when the unit is turned off, the absence of the unit is informed to a home location register. In this method, when the intensity of electric field becomes weaker than a predetermined value, detaching operation is performed and when the intensity of electric field become stronger than the predetermined value, attaching operation is performed. A subscriber terminal unit that has entered in a low or high intensity area does not always stay in the area. Thus, when the subscriber terminal unit is present at the boundary of the low intensity area and the high intensity area, the subscriber terminal unit repeats the detaching operation and the attaching operation. Consequently, when the detaching method is used, the number of signals that are transmitted between subscriber terminal units and the mobile communication network increases, thereby congesting the communication channels of the network.
In a conventional location updating system, while the location of each subscriber terminal unit is updated among mobile communication networks, it is not updated among networks including wired communication networks. Thus, there is a case that even if there is a wired telephone is present in the subscriber's neighbor, a call in process to the subscriber is performed through a mobile communication network. To prevent this problem, each subscriber have to inform the telephone number of the wired telephone to people who may call the subscriber. Thus, each subscriber has to spend a lot of time and money.
In addition, in a conventional location updating system, when the service area becomes wide with the introduction of a roaming service or the like or when the service area is subdivided so as to improve the efficiency of frequency utilization, whenever the location registered area of each terminal unit varies, the location thereof is updated. Thus, the number of signals that are transmitted between each subscriber terminal unit and the mobile communication network increases, thereby congesting the communication channels of the network.
Moreover, in a conventional location tracking system, while each subscriber is traveling, accurate tracking information cannot be obtained. Thus, tracking information sometimes does not match the place where each subscriber is present. In this case, the response for a call in is not obtained. In other words, there are wasteful call ins.
Furthermore, in a conventional location tracking system, there is a service that allows each subscriber to change tracking information. Subscribers who frequently travel and change their schedules frequently change tracking information. Since tracking information of such subscribers has much changed information, the number of signals that are transmitted between each subscriber terminal and the mobile communication network increases, thereby congesting the communication channels of the network.